Lotus Elan and Lotus Elan Plus 2 Forums

I wish to know, to improve in pressure the oil pump?
how to modify , have you already done it?

You can buy a spring kit to increase the pressure of your oil pump.
But what is your reason for doing it?
Increasing the pressure will not increase the pressure seen when the oil is hot and the engine is idling even in an excellent condition engine with good bearing clearances, plus it puts more load on the skew gear of the pump and jackshaft.

Good way to get even more impressive oil leaks

I have always been told by various Elan experts that there is no point in fitting a high pressure pump to a standard tune twin cam and it will also put extra pressure on the oil seals. Interestingly, my car has a new standard pump fitted to a standard fully rebuilt engine and it reads 45 psi when hot.

Generally Twink oil leaks have nothing to do with oil pressure. Typically twinks suffer from perceived low hot oil pressure at idle. Provided its over about 15psi at idle hot I would not worry as long as you get 35 to 40 psi when hot above around 2000 rpm.

The standard twink relief valve on the pump is supposed to open at 40 psi and will normally be open at idle rpm when the oil is cold and this will be limiting the pressure to around 40 psi. Whether the relief valve opens when the engine is hot depends on engine bearing wear and pump wear but with a good pump and good bearings you should see 40 psi when the engine is hot above around 2000 rpm as the pump relief valve will still open.

As the engine bearings wear and the pump wears the pump will need more and more rpm to get to opening the relief valve when hot and the pressure will be lower at idle.

Replacing the pump relief valve spring with a higher pressure one will increase the pressure and flow at idle when cold but make no difference when hot as the normal relief valve spring does not open. At higher revs when the engine is cold or hot it will increase the pressure ( and thus flow) and revs at which the relief valve opens. This may be advantageous in a high rev engine when looking for higher pressure and flow at the top end but is not required in a standard engine.

regards
Rohan

From notes made at a meeting at Ford Competition Department Rainham 1965 discussing TwinCams as competition engines.
Oil Pump.
The oil pump is supplied by Hobourn Eaton and is modified and built from selected parts to Ford requirements. The pump is uprated to a pressure of 65-70 psi.

Yes in competition engines a high volume high pressure pump is often used. A standard volume but higher pressure pump can also be used but its benefit is doubtful in a competition engine as it will not deliver more volume in many circumstances when its needed.

A standard volume / standard pressure pump is all you need in a road twin cam with the correct bearing clearances. Maybe a high volume / high pressure pump or standard volume / high pressure pump will help compensate for worn bearings in some circumstance but its really just hiding a bigger problem

cheers
Rohan

You really only need a high pressure oil pump if you are revving the engine for long periods over 6,500RPM (eg. competition use). For any given bearing clearance high pressure results in higher oil flow which results in better bearing cooling.
Note for standard Ford oil pumps (i.e not those described as high volume) there are two rotor widths available. The earlier non spin on filter pump has narrower rotor lobes and hence lower volume flow rate than the later spin on filter type so fitment of a later type pump is a slight upgrade if your engine is currently fitted with the earlier type.
Note that some high volume / high pressure pumps are only advertised as being suitable for engines not revved much over standard which rather defeats the purpose. This is because the heavier rotors and thicker heavier end plate can lead to the pump housing cracking at the high vibration levels experienced at high RPM. I believe the solution is to use sealant rather than a gasket between pump and block (as Rohan does) or replace the heavy steel end plate with an aluminium one such as this:

http://initracing.co.uk/parts-for-sale/ ... n-cam-oil/

One aspect of oil pumps and oil pressure that is overlooked is the flow of oil through the pump and into the oil passageways. We would not tolerate the obstructions and sharp edges in the inlet manifold so why tolerate them in the oil inlet?
It you dismantle the oil pump and study it you can see where the flow can be improved by 'blending' the port shapes. The oilway entry into the block can be quite restrictive also and time spent with a Dremel or similar tool here will help flow. Blending the pump outlet to the block inlet using the gasket as a pattern helps. The time to do all this work is before the final clean up of the engine components of course! There is nothing usually we can do about the restrictive flow inside the block and crank although modern designers have found ways.

thank you for sharing